Rescue efforts in South Africa have been suspended at the site a collapsed half-built mall, police say.
Police spokesperson Thulani Zwane told the BBC that the search for survivors would resume after some of the concrete blocks were cleared.
One person has died and there are fears that some construction workers, possibly 40, are trapped in the rubble at the site in Tongaat town.
About 30 people have been rescued, some with traumatic injuries, medics say.
Capt Zwane said 11 of those taken to hospitals in the area are critically injured.
The police had also opened a case of culpable homicide following the death of one women in the collapse, he said.
The deputy mayor of the municipality told South African media that authorities had obtained an injunction a month ago to halt construction at the site in Tongaat, which is a small town about 40km (25 miles) north of Durban.
"There are areas of the law that they [construction firms] did not follow in terms of building," Nomvuzo Shabalala told broadcaster ENCA.
"We were not aware that they were continuing building," she added.
On Wednesday morning, engineers from the department of labour arrived and are now using heavy machinery to remove concrete blocks.
Medics say the collapsed roof is about the size of a rugby field.
The department of labour, which is now leading the operation, says work will continue throughout the night and it is hoped all the rubble and debris will have been removed by Thursday morning.
Overnight on Tuesday six different rescue teams alternated shifts, working in the dark and using sniffer dogs and fibre-optic cameras to try to find survivors.
Neil Powell, a member of the rescue team, said eyewitnesses had given their account of how the accident happened at the construction site, which is in the town's centre, near a railway.
"They're saying that apparently scaffolding underneath the concrete slabs fell and collapsed, which caused the concrete slabs to fall and trap the workers," Mr Powell of Crisis Medical, an emergency service provider in Durban, told the BBC's Newsday programme.
Fiona Moonean, who lives across from the building site, was washing dishes when she heard a "thunderous noise" coming from outside.
"There was this sound, it was too huge, that I picked my head up - at that point I just saw the whole slab - that just came down and all you could hear was the guys screaming," she told the AFP news agency.